The uptake of renewable natural resources (renewables) for energy generation in the last years has been impressive, but there is still the unsolved problem of dealing with the transient nature of the renewables. Both solar and wind power are intermittent by their nature and, therefore, it is not possible to provide a dependable baseload to the energy networks. Since the demand of energy consumers can be irregular, a power supply based on renewables does not match the demand of the consumers. Also, the excess energy, i.e. the amount of energy which would be momentarily available from renewables but which is not demanded by the consumers at that time, strains the energy networks and would get lost in case it is not consumed.
Thus, conditions exist in which the energy momentarily provided by renewables is not sufficient to cover the demand. However, there would also be conditions in which the energy momentarily provided by renewables is exceeding the current demand. As the proportion of energy from renewable sources increases, the situation will become unsustainable.
A promising approach for solving these drawbacks would be the use of long term energy buffers or storages which are suitable to store the energy. Such a solution would allow to handle situations in which the demand exceeds the available energy as well as situations in which excess energy is available.
A variety of buffering solutions for storing electrical energy are known, e.g. Lithium batteries and Vanadium based Redox batteries, but these solutions cannot provide the necessary scale of energy storage. Hydrogen offers another carbon free route for storing energy, but it is difficult and risky to utilize. In gaseous form it has to be compressed to 500 bars in order to achieve a suitable energy density. Liquid Hydrogen requires cryogenic temperatures and the associated complicated infrastructure. Moreover, the use of Hydrogen in either form requires safeguards due to the risk of explosion. For these reasons, Hydrogen is not considered to be a qualified candidate for energy storage.
Thus, there are currently no reliable and appropriate means for decoupling energy supply and demands for renewable energies on a local or national scale.